Nonpatent Literature 1 (Journal of Crystal Growth, 264 (2004), pp. 53-57) discloses a quantum well structure grown on a c-plane sapphire substrate. The supplying of TMIn is performed to before growing an InGaN layer.
Nonpatent Literature 2 (Japanese Journal of Applied Physics, Vol. 47, No. 2 (2008) pp. 829-842) discloses an InGaN/GaN multiple quantum well structure grown on a c-plane sapphire substrate. In the formation of the multiple quantum well structure, after growing a GaN barrier layer at a first growth temperature, the substrate temperature is lowered to a second growth temperature for the well layer. After the substrate temperature has been lowered, indium is supplied onto the GaN barrier layer at the second growth temperature, and then an InGaN well layer is grown thereon. Just after having growing the InGaN well layer, a GaN cap layer is grown on this well layer. The growth of the GaN cap layer is performed while the temperature is raised from the second growth temperature to the first growth temperature. After growing the GaN cap layer, the growth is interrupted at the first growth temperature. Then, another GaN barrier layer is grown on the GaN cap layer. The supply of indium does not affect the indium content and abruptness at the surface boundary in the InGaN/GaN structure. This process, i.e., the supply of InGaN, ensures a decrease in density of V-shaped defects in the InGaN/GaN quantum structure.
Nonpatent Literature 3 (Applied Physics Letters, Vol. 92 (2008) 161113) discloses an InGaN/GaN quantum well structure grown on a c-plane sapphire substrate. A quantum well layer and a barrier layer are grown at a temperature of 780° C. In the growth of the quantum well structure, TMIn and ammonia are supplied to a reactor after the growth of the InGaN well layer and before the growth of the GaN barrier layer. This step reduced the density of V-shaped defects from 3.9×108 to 2.9×108 cm−2 in a single quantum well structure, and from 7.8×108 to 4.7×108 cm−2 in a multiple quantum well structure.